Companies have been asked to stop selling all forms of the heartburn drug Zantact, after the US Food and Drug Administration found low levels of a 'potentially dangerous' cancer-causing chemical in them late last year. Consumers were warned to stop taking any over-the-counter forms of the drug such as ranitidine. The contaminant that was found in Zantac was ascertained to be a type of cancer-causing NDMA. The FDA has found that the contaminants in some products increase over time and when stored at higher than room temperatures and may result in exposure to unacceptable levels of this impurity. It advised consumers to consult their doctors before stopping the medication and chosing an alternative.